Interhemispheric functional connectivity in primary insomnia: a resting-state funtional MRI study

Abstract

Objective To investigate the resting-state functional connectivity between the two hemispheres in primary insomnia(PI) using voxel-mirrored homotopic connectivity(VMHC) based on restingstate functional MRI(fMRI).Methods Eighteen PI patients and 19 healthy volunteers matched for age and sex underwent resting-state fMRI scans in a 1.5T scanner.Pittsburgh sleep quality index(PSQI) was performed for all subjects.The data was pre-processed by SPM 8 and then the VMHC values were calculated by REST software.The VMHC values between the two groups were compared by two-sample t-test.The statistical map with significant differences of VMHC value was obtained.Results Compared to the controls,PI patients showed significant VMHC decreases in the middle frontal gyrus(MFG),superior frontal gyrus(SFG),orbitofrontal cortex(OFC),hippocampus,thalamus,insula and a few occipital regions including cuneus and lingual gyrus(voxel size 1 269-7 425 mm3,t=-4.47-2.74 P＜ 0.05,Alphasim corrected).Negative correlation was observed between VMHC coefficients(0.324±0.247) of OFC and the PSQI score (10.1 ± 1.7) in PI patients(r=-0.69,P＜0.01).The other regions showing significant VMHC changes had no correlation with the PSQI score(P＞0.05).Conclusions These findings suggest that the functional coordination between homotopic brain regions is impaired in PI patients.Interhemispheric RSFC may serve as a useful method for evaluating PI where neural connectivity is implicated in the pathophysiology. Key words: Sleep initiation and maintenance disorders; Magnetic resonance imaging; Neural networks(computer)